In the area of the transfer of inductive energy to movable consumers, for example, electric land vehicles, such as automobiles or trucks, a method is known for charging its vehicle battery via a stationary primary coil of a charging station and a secondary coil located on the bottom of the vehicle. The primary coil is thereby located on or in the traveling lane, for example, on publicly accessible parking lots, charging areas of filling stations, or in the garage of the owner of the vehicle. For the charging operation, the electric vehicle is driven over the primary coil, so that the secondary coil that is located in the vehicle is aligned on the primary coil.
DE 10 2009 033 236 A1 discloses an example for this, in which the secondary coil is located, together with a ferrite plate as a flux guide unit, in a housing on the bottom of an electric vehicle.
DE 10 2008 029 200 A1 discloses a body of a motor vehicle with at least one structure area formed from a plate element. The plate element is located on the bottom of the vehicle body and, in the longitudinal direction, has longitudinal hollow chambers located in the transverse direction of the motor vehicle, next to one another, into which energy storage elements, in particular, accumulator batteries, or other components of an energy storage device are placed. In order to reduce damage or destruction of the energy storage device with the resulting endangerment of the vehicle occupants in case of an accident of the motor vehicle, the energy storage elements, for example, are located only in areas which cannot be deformed excessively in case of an accident, for example, only under the driver's seat, located centrally. In this way, not only the front and rear structures, but also the lateral areas of the passenger compartment, can be deformed for the energy absorption, whereas the energy storage elements are not located in these areas.
DE 10 2007 040 770 A1 discloses a passenger car with a vehicle bottom with a middle tunnel, which extends in the longitudinal direction of the vehicle. The middle tunnel has at least one weak site, where the middle tunnel is deformed under the effect of force caused by an accident after a stress limit has been exceeded. No indication is made there of a coil unit with a flux guide unit for the inductive transfer of electrical energy between the coil unit and a stationary charging station.
DE 10 2010 035 634 A1 discloses a transfer system for charging the traction batteries of an electric vehicle with a coupling device that is attachable thereon, with a transformer part, by means of which the electrical energy can be transferred inductively to a transformer part on the vehicle. The transformer part, which is integrated in the vehicle license plate, has a coupling body made of a flexible plastic material, which surrounds an electrical coil arrangement with a ferrite arrangement, consisting of plate- or yoke-like ferrites, separated from one another. The ferrites, separated from one another, worsen the magnetic flux guidance and thus the coupling between the transformer parts.
With the known coil units, the disadvantage is that the magnetic flux guide unit, as a rule, is made of a massive, rigid, and heavy material, for example, a ferrite plate. Since the coil unit is usually arranged, parallel to the surface, on the bottom of the vehicle and exhibits a great inertia because of its heavy weight, the danger with a rear-end collision is that the flux guide unit will be hurled in the direction of the impact zone and the coil unit will be thereby destroyed and perhaps travel from its anchorage on the bottom of the vehicle and will damage the vehicle and endanger the vehicle occupants as well as persons found outside the vehicle. Since the flux guide unit is also very rigid, as a rule, it will also transfer the impact energy, more or less undiminished, in case of a collision.